Effect of different levels of selenium and vitamin E injection on thyroid hormones ‎metabolism and biochemical parameters in late pregnancy of Holstein cows and their ‎calf performance ‎

To compare the effects of injection different levels of selenium and vitamin E in late pregnancy on thyroid hormone metabolism and biochemical parameters of Holstein cows and their calf performance, 28 pregnant Holstein cows were selected in 8 weeks before calving and randomly assigned to 4 treatments and 7 replications. Cows were then injected with selenium and vitamin E four and two weeks before the expected time for calving. Treatments included: injection of 0 (contro), 15, 30 and 45 ml of selenium and vitamin E supplements. Each ml of supplement contained 0.5 mg of selenium in the form of sodium selenite salt and 50 international units of vitamin E in the form of DL alpha tocopherol acetate. Cows were balanced in terms of age, weight and calving time. The results showed that injection of selenium and vitamin E in pregnant cows affected the weight performance of their calves (P<0.05) so that the daily weight gain and weight of calves at 30 and 45 days of age in Selenium and vitamin E treatments increased, compared to the control group (P<0.05). Receiving of selenium and vitamin E makes pregnant cows resistant to low blood glucose and triglycerides in the postpartum period. At one week after delivery. The concentration of glucose and blood triglycerides in the injected cows increased compare to the control treatment (P<0.05). Also, one week before and after delivery, with increasing the dose of selenium and vitamin E, the activity of glutathione peroxidase and the concentration of tetrahydrotyronine and triiodothyronine increased (P<0.05). In general, according to the present results, at least 30 ml of selenium and vitamin E at the end period of pregnancy for Holstein cows, could be recommended.